The harnessing of solar energy is often mentioned as a partial solution to the world's energy problems because an enormous amount of solar energy reaches the earth's surface every day. Practical problems, however, have limited the harnessing of the sun's energy for use as electrical or chemical power to run machinery. While the total sun's energy reaching the earth at any one time is tremendous, the amount reaching any specific area is relatively small. In order therefore to collect solar energy in significant amounts, it must be collected over a large surface area so a solar energy collection facility will cover a large area. Additional problems in making solar energy practical include the fact that while the sun's energy can be gathered by thermal receptors, concentrating the heat is difficult. While solar energy has been utilized efficiently where a moderate heat reservoir is required, e.g., hot water in homes, generators for electricity require large temperature differences between a high temperature reservoir and a low temperature reservoir to operate efficiently.
The photovoltaic cell has long been known as a device for converting light rays to electricity. The use of photovoltaic cells, except in specialized applications, has not been practical for the production of electricity because it produces direct current at low voltage and does so inconsistently, i.e. primarily when the sun shines.
An alternative solution is to convert photoelectric energy to chemical energy, and one way to do this is by using electricity produced by photoelectric cells to produce hydrogen from the electrolysis of water. Hydrogen so produced may be used as an energy source in fuel cells or as a clean, burnable fuel which produces only water when burned. By converting photoelectric energy to storable hydrogen, a consistent source of energy is provided which is independent of the variations in available light. A solar energy to hydrogen conversion system can be set up anywhere, and although the amount of energy produced is, of course, dependent on the available sunlight, energy can potentially be provided at a location near the site where the energy is to be utilized.
The problem remains, however, that a large surface area is necessary for the conversion of the sun's energy into electricity and thereafter to hydrogen by electrolysis. A facility for producing significant amounts of hydrogen would require tremendous areas. The large surface areas covered could make maintenance problems difficult, and a widely spread grid of solar receptors would be subject to damage by the elements.